Carboxy-functionalized polyphenylene ethers and blends containing them

ABSTRACT

Carboxy-functionalized polyphenylene ethers containing structural units with a carboxyalkyl group in the 2-position are prepared by redistribution of a polyphenylene ether with a 2-carboxyalkylphenol such as 2-(3-carboxypropyl)phenol (melilotic acid), or by oxidative coupling of a suitable phenol with such a 2-carboxyalkylphenol. The products form compatibilizing copolymers with polymers containing carboxylic acid-reactive functional groups, such as polyesters, polyamides and epoxy resins.

BACKGROUND OF THE INVENTION

[0001] This invention relates to polyphenylene ethers, and moreparticularly to functionalized polyphenylene ethers useful for thecompatibilization of copolymer blends.

[0002] Polyphenylene ethers are a widely used class of thermoplasticengineering resins characterized by excellent properties includinghydrolytic stability, dimensional stability, toughness, heat resistanceand dielectric properties. It is of continuing interest to introducethese desirable properties into polymer blends by incorporating thepolyphenylene ethers as blend constituents. This is often difficult,however, since the polyphenylene ethers are incompatible with many otherpolymers.

[0003] A strategy frequently used to compatibilize polyphenylene etherswith other polymers is to introduce into the polyphenylene etherfunctional groups which are reactive with said other polymers, enablingthe formation of copolymer-containing compositions in which thecopolymers serve as compatibilizers. For example, polyphenylene etherscontaining carboxylic acid functional groups or derivatives thereof canform copolymers with such other polymers as polyamides,hydroxy-terminated polyesters and epoxy group-containing polymers.

[0004] Carboxy or carboxy-derived groups (e.g., anhydride groups) havebeen introduced into polyphenylene ethers by reaction through thehydroxy end groups with such compounds as trimellitic anhydride acidchloride, by grafting reactions with such compounds as maleic anhydrideor fumaric acid, and by redistribution with acidic compounds such asp-hydroxyphenylacetic acid. Redistribution reactions are often ofparticular interest since they may be conducted under relatively mildconditions, typically including temperatures not substantially greaterthan 100° C. and the presence of non-destructive catalysts such asdiaryl peroxides and quinones and relatively inert solvents such astoluene. The redistribution reaction results in a breakup of polymermolecules into lower molecular weight molecules containing the desiredcarboxylic acid or other functional groups.

[0005] Redistribution with the aforementioned acidic compounds issomewhat difficult, however, since said compounds are not adequatelysoluble in solvents such as toluene. Moreover, the mechanism of theredistribution reaction is such that only low levels of such compoundscan be incorporated in the polyphenylene ether, owing in part tosubstitution in the para position which makes that position unavailablefor reaction.

[0006] Copending, commonly owned application Ser. No. 08/800,694discloses attempts at redistribution of polyphenylene ethers withvarious aryl-substituted alkanoic acids. It was found that whereascarboxy phenols bearing two phenolic hydroxyl groups and alkylsubstituents ortho to the phenolic hydroxy groups, such as4,4-bis(3,5-dimethyj-4-hydroxyphenyl)pentanoic acid, did incorporate,simple phenols such as p-hydroxyphenyloctanoic acid did not. Interestcontinues, therefore, in the development of improved functionalizationstrategies employing other carboxylic acids, especially those of simplermolecular structure than the aforementioned bisphenolic acid.

[0007] Japanese Kokai 5/59,270 and 5/59,272 disclose reaction productsof epoxy- and carboxy-functionalized olefin polymers withcopolyphenylene ethers in which a portion of the structural unitscontain a —(CH₂)₃OH group. Said copolyphenylene ethers are produced bycopolymerization via oxidative coupling of two phenols, one containingand one not containing said group. There is no disclosure of acopolyphenylene ether containing a carboxyalkyl group.

SUMMARY OF THE INVENTION

[0008] The present invention is based on the discovery that certaino-hydroxyaromatic-substituted aliphatic carboxylic acids are capable ofincorporation under mild conditions into polyphenylene ethers, either bycopolymerization or by redistribution. The conditions employed includeuse of a single solvent in which the polyphenylene ether has highsolubility.

[0009] One aspect of the invention, therefore, is carboxy-functionalizedpolyphenylene ethers comprising structural units of the formulas

[0010] wherein each Q¹ is independently halogen, primary or secondarylower alkyl, phenyl, haloalkyl, aminoalkyl, hydrocarbonoxy, orhalohydrocarbonoxy wherein at least two carbon atoms separate thehalogen and oxygen atoms; each Q² and Q³ is independently hydrogen,halogen, primary or secondary lower alkyl, phenyl, haloalkyl,hydrocarbonoxy or halohydrocarbonoxy as defined for Q¹; and R is analkylene radical containing at least 1 carbon atom.

[0011] A further aspect of the invention is a method for preparation ofsuch functionalized polyphenylene ethers which comprises redistributinga polyphenylene ether with a 2-carboxyalkylphenol of appropriate formula(corresponding to formula II) in the presence of a redistributioncatalyst.

[0012] Another aspect of the invention is a method for production ofsuch functionalized polyphenylene ethers which comprises oxidativelycoupling at least one monohydroxyaromatic compound with said2-carboxyalkylphenol.

[0013] These carboxy-functionalized polyphenylene ethers are reactiveand readily form copolymers with other reactive polymers. Therefore, astill further aspect of the invention is resinous compositionscomprising copolymers of said functionalized polyphenylene ethers withat least one polymer containing carboxylic acid-reactive functionalgroups.

DETAILED DESCRIPTION; PREFERRED EMBODIMENTS

[0014] The polyphenylene ethers which are functionalized according tothe invention are known polymers having structural units of formula I.Both homopolymer and copolymer polyphenylene ethers are included. Thepreferred homopolymers are those containing 2,6-dimethyl-1,4-phenyleneether units. Suitable copolymers include random copolymers containingsuch units in combination with (for example)2,3,6-trimethyl-1,4-phenylene ether units. Also included arepolyphenylene ethers containing moieties prepared by grafting onto thepolyphenylene ether in known manner such materials as vinyl monomers orpolymers such as polystyrenes and elastomers, as well as coupledpolyphenylene ethers in which coupling agents such as low molecularweight polycarbonates, quinones, heterocycles and formals undergoreaction in known manner with the hydroxy groups of two polyphenyleneether chains to produce a higher molecular weight polymer, provided asubstantial proportion of free OH groups remains.

[0015] The polyphenylene ethers generally have an intrinsic viscositygreater than about 0.25, most often in the range of about 0.25-0.6 andespecially 0.4-0.6 dl./g., as measured in chloroform at 25° C.

[0016] The polyphenylene ethers are typically prepared by the oxidativecoupling of at least one monohydroxyaromatic compound such as2,6-xylenol or 2,3,6-trimethylphenol. Catalyst systems are generallyemployed for such coupling; they typically contain at least one heavymetal compound such as a copper, manganese or cobalt compound, usuallyin combination with various other materials.

[0017] Particularly useful polyphenylene ethers for many purposes arethose which comprise molecules having at least one aminoalkyl-containingend group. The aminoalkyl radical is covalently bound to a carbon atomlocated in an ortho position to the hydroxy group. Products containingsuch end groups may be obtained by incorporating an appropriate primaryor secondary monoamine such as di-n-butylamine or dimethylamine as oneof the constituents of the oxidative coupling reaction mixture. Alsofrequently present are 4-hydroxybiphenyl end groups and/or biphenylstructural units, typically obtained from reaction mixtures in which aby-product diphenoquinone is present, especially in acopper-halide-secondary or tertiary amine system. A substantialproportion of the polymer molecules, typically constituting as much asabout 90% by weight of the polymer, may contain at least one of saidaminoalkyl-containing and 4-hydroxybiphenyl end groups.

[0018] It will be apparent to those skilled in the art from theforegoing that the polyphenylene ethers contemplated for use in thepresent invention include all those presently known, irrespective ofvariations in structural units or ancillary chemical features.

[0019] The functionalized polyphenylene ethers of the invention contain,in addition to structural units of formula I, those of formula II inwhich Q¹⁻³ are as previously defined. The units of formula II arecharacterized by a carboxyalkyl group in the 2- or 3-position,preferably the 2-position, relative to the oxygen atom and a Q² moietyin the other of the 2- and 3-positions. The R radical in saidcarboxyalkyl group is an alkylene radical containing at least 1 andpreferably 2-6 carbon atoms; it may be linear or branched and is usuallylinear. Particularly preferred is the ethylene radical, whereupon thecorresponding carboxylic acid is 2-(3-carboxypropyl)phenol (meliloticacid).

[0020] The first method of the invention for preparation of thefunctionalized polyphenylene ethers is by redistribution of aconventional polyphenylene ether with the appropriate2-carboxyalkylphenol; i.e., the compound corresponding to formula 11(hereinafter sometimes simply “acid” for brevity). Redistribution may beeffected as described, for example, in U.S. Pat. No. 3,367,978,4,234,706 and 5,213,886 and in White et al. J. Org. Chem., 34, 297-303(1969), the disclosures of which are incorporated by reference herein.

[0021] The redistribution reaction typically involves heating thepolyphenylene ether in solution in a relatively inert solvent, mostoften an aromatic hydrocarbon such as toluene or xylene, with the acidand a redistribution catalyst at a temperature in the range of about50-110° C. Suitable redistribution catalysts include peroxides such asbenzoyl peroxide, cumyl peroxide, t-butylperbenzoic and t-butylalkanoicacids and quinones such as 3,3′,5,5′-tetramethyl-4,4′-diphenoquinone(TMDQ).

[0022] Redistribution is accompanied by cleavage of the polymer moleculeby the acid, which is incorporated in the cleaved molecules, most oftenas an end group at the head of the molecule. The proportion of acid isdetermined by the degree of functionalization desired coupled with theoverall molecular weight desired in the product; high proportions ofacid result in a high degree of functionalization and a lower averagepolymer molecular weight, while low proportions afford a highermolecular weight polymer with a low degree of functionalization. Ingeneral, acid levels are in the range of about 1-10% and preferablyabout 2-5% by weight based on polyphenylene ether. The promoter is mostoften employed in the amount of about 1-10% by weight based onpolyphenylene ether.

[0023] The second preparative method of the invention iscopolymerization of the acid in suitable proportions with at least onemonohydroxyaromatic compound, i.e., the one corresponding to formula I,in an oxidative coupling reaction. The conditions of said reaction arethe art-recognized ones, typically including the presence of a catalystof oxidative coupling as previously described. An advantage of thismethod of preparation may be the ease of preparing functionalizedpolyphenylene ethers of relatively high molecular weights.

[0024] The resinous compositions of the invention may be prepared byeffecting reaction between the carboxy-functionalized polyphenyleneether and any polymer containing one or more functional groups which arereactive with carboxylic acids. Illustrative groups of this type arehydroxy, amino and epoxy groups. Said polymer may be thermoplastic orthermosetting. Examples of suitable polymers are hydroxy-terminatedpolyesters, amine-terminated polyamides, and epoxy resins includingglycidyl ethers of bisphenols, epoxy-functionalized olefin polymers,epoxy novolaks and alicylic epoxy resins.

[0025] The reaction of the polymer with the carboxy-functionalizedpolyphenylene ether may take place under any suitable conditions,including solution and melt reaction conditions. Where appropriate, theymay be conducted in the presence of suitable catalysts, as illustratedby phase transfer catalysts and epoxy cure catalysts. Other materials,both reactive and non-reactive, may be present. Illustrative materialsare impact modifiers, hardeners, fillers, pigments and stabilizers.

[0026] The invention is illustrated by the following examples. All partsand percentages are by weight. Molecular weights are weight averageunless otherwise indicated and were determined by gel permeationchromatography. Inherent viscosities were determined in chloroform at25° C. Carboxy incorporation was determined by proton nuclear magneticresonance spectroscopy.

EXAMPLES 1-4

[0027] Samples (20 g each) of a poly(2,6-dimethyl-1,4-phenylene ether)having a weight average molecular weight of about 50,100 and an inherentviscosity of 0.40 dl/g and 800 mg of melilotic acid were dissolved in100 ml of toluene. Various amounts of benzoyl peroxide were added andthe mixtures were heated at 90° C for 90 minutes. They were then cooledand the functionalized polyphenylene ethers were precipitated byaddition of methanol, filtered and dried overnight in vacuum. Theresults are given in Table I. TABLE I Example 1 2 3 4 Benzoyl peroxide,g 0.40 0.80 1.20 1.60 Product Mw 18,900 16,000 13,700 12,200 Product Mn 6,400  5,400  3,300  3,000 Carboxy content, μmol/g   106   123   140  146 Carboxy incorporation, %    44    51    58    61

EXAMPLES 5-7

[0028] The procedure of Examples 1-4 was repeated, substituting TMDQ forthe benzoyl peroxide. The results are given in Table II. TABLE IIExample 5 6 7 TMDQ, g 0.20 1.20 1.60 Product Mw 16,100 11,600 11,700Product Mn  4,300  3,500  3,300 Carboxy content, μmol/g   117   161  154 Carboxy incorporation, %    49    67    64

EXAMPLE 8

[0029] A 50% solids solution in toluene was prepared from 31 parts ofthe carboxy-functionalized polyphenylene ether of Example 2, 37.8 partsof a tetrabromobisphenol A diglycidyl ether sold by Dow Chemical underthe product designation “DER 542”, 17.6 parts of a copolymer ofbisphenol A and tetrabromobisphenol A diglycidyl ether, 17.6 parts of anepoxy novolak sold by Ciba Geigy under the product designation “EPN1138”, 3.64 parts of zinc octanoate, 0.33 part of2-ethyl-4-methylimidazole and 0.84 part of diaminodiethyltoluene. A 7628E-style glass fiber fabric was impregnated with the solution and theimpregnated fabric was heated at 150° C. for 7 minutes to remove solventand partially cure the epoxy resins. Six plies of the resultingreinforced prepreg were layered and heated in a compression mold at 200°C. for 3 hours. The product was a laminate having the followingproperties:

[0030] Resin content—27.08%;

[0031] Solvent resistance (methylene chloride)—good;

[0032] Tg—190° C.;

[0033] Dielectric constant—4.7;

[0034] Dissipation factor—0.0061;

[0035] Flammability (UL-94)—V-0.

What is claimed is:
 1. A carboxy-functionalized polyphenylene ethercomprising structural units of the formulas

wherein each Q¹ is independently halogen, primary or secondary loweralkyl, phenyl, haloalkyl, aminoalkyl, hydrocarbonoxy, orhalohydrocarbonoxy wherein at least two carbon atoms separate thehalogen and oxygen atoms; each Q² and Q³ is independently 10 hydrogen,halogen, primary or secondary lower alkyl, phenyl, haloalkyl,hydrocarbonoxy or halohydrocarbonoxy as defined for Q¹; and R is analkylene radical containing at least 1 carbon atom.
 2. A polyphenyleneether according to claim 1 wherein Q² is in the 3-position relative tothe oxygen atom and RCOOH is in the 2-position.
 3. A polyphenylene etheraccording to claim 2 wherein each Q¹ is methyl and each Q² is hydrogen.4. A polyphenylene ether according to claim 3 wherein each Q³ ishydrogen.
 5. A polyphenylene ether according to claim 4 wherein R is alinear alkylene radical containing 2-6 carbon atoms.
 6. A polyphenyleneether according to claim 5 wherein R is ethylene.
 7. A method forpreparing a functionalized polyphenylene ether according to claim 1which comprises redistributing a polyphenylene ether with a2-carboxyalkylphenol in the presence of a redistribution catalyst.
 8. Amethod according to claim 7 wherein the 2-carboxyalkylphenol ismelilotic acid.
 9. A method according to claim 7 wherein theredistribution catalyst is a peroxide or a diphenoquinone.
 10. A methodaccording to claim 9 wherein the redistribution catalyst is benzoylperoxide.
 11. A method according to claim 9 wherein the redistributioncatalyst is 3,3′,5,5′-tetramethyl-4,4′-diphenoquinone.
 12. A methodaccording to claim 9 wherein the redistribution temperature is in therange of about 50-110° C.
 13. A method for preparing a functionalizedpolyphenylene ether according to claim 1 which comprises oxidativelycoupling at least one monohydroxyaromatic compound with said2-carboxyalkylphenol.
 14. A method according to claim 13 wherein the2-carboxyalkylphenol is melilotic acid.
 15. A method according to claim13 wherein the monohydroxyaromatic compound is 2,6-dimethylphenol.
 16. Aresinous composition comprising a copolymer of a functionalizedpolyphenylene ether according to claim 1 with at least one polymercontaining carboxylic acid-reactive functional groups.
 17. A resinouscomposition according to claim 16 wherein the polymer is thermoplastic.18. A resinous composition according to claim 17 wherein the polymer isa hydroxy-terminated polyester or an amine-terminated polyamide.
 19. Aresinous composition according to claim 16 wherein the polymer isthermosetting.
 20. A resinous composition according to claim 19 whereinthe polymer is at least one epoxy resin.